Time scales of transient enhanced diffusion: Free and clustered interstitials

Transient enhanced diffusion (TED) and electrical activation after nonamorphizing Si implantations into lightly B-doped Si multilayers shows two distinct timescales, each related to a different class of interstitial defect, At 700 degrees C, ultrafast TED occurs within the first 15 s with a B diffusivity enhancement of > 2 x 10(5), Immobile clustered B is present at low concentration levels after the ultrafast transient and persists for an extended period (similar to 10(2) - 10(3) s), The later phase of TED exhibits a near-constant diffusivity enhancement of approximate to 1 x 10(4), consistent with interstitial injection controlled by dissolving {113} interstitial clusters. The relative contributions of the ultrafast and regular TED regimes to the final diffusive broadening of the B profile depends on the proportion of interstitials that escape capture by {113} clusters growing within the implant damage region upon annealing. Our results explain the ultrafast TED recently observed after medium-dose B implantation, In that case there are enough B atoms to trap a large proportion of interstitials in Si-B clusters, and the remaining interstitials contribute to TED without passing through an intermediate {113} defect stage, The data on the ultrafast TED pulse allows us to extract lower limits for the diffusivities of the Si interstitial (D-1 > 2 x 10(-10) cm(2)s(-1)) and the B interstitial(cy) defect (D-Bi > 2 x 10(-13) cm(2)s(-1)) at 700 degrees C.